The U.S. has set as a national goal the narrowing of the achievement gap between lower income and middle-class students, and that between racial and ethnic groups. This is a key purpose of the No Child Left Behind act, which relies primarily on assessment to promote changes within schools to accomplish that goal. However, out-of-school factors (OSFs) play a powerful role in generating existing achievement gaps, and if these factors are not attended to with equal vigor, everyone's national aspirations will be thwarted. This brief details six out-of-school factors (OSFs) common among the poor that significantly affect the health and learning opportunities of children, and accordingly limit what schools can accomplish "on their own": (1) low birth-weight and non-genetic prenatal influences on children; (2) inadequate medical, dental, and vision care, often a result of inadequate or no medical insurance; (3) food insecurity; (4) environmental pollutants; (5) family relations and family stress; and (6) neighborhood characteristics. These OSFs are related to a host of poverty-induced physical, sociological, and psychological problems that children often bring to school, ranging from neurological damage and attention disorders to excessive absenteeism, linguistic underdevelopment, and oppositional behavior. Also discussed is a seventh OSF, extended learning opportunities, such as preschool, after school, and summer school programs that can help to mitigate some of the harm caused by the first six factors. (Contains 7 figures, 6 tables, and 157 notes.)